The present disclosure relates to an organic electroluminescence (EL) display device that performs image displaying by utilizing an organic electroluminescence phenomenon and electronic apparatus including such an organic EL display device.
As development of the information communication industry is accelerated, display elements having higher performance are required. Among the display elements, the organic EL element, which is attracting attention as a next-generation display element, has not only advantages of having a wide viewing angle and being excellent in the contrast as a self-luminous display element but also an advantage of having a short response time.
The materials of the functional layers, such as a light emitting layer, to form the organic EL element are classified broadly into low-molecular materials and polymer materials. As the film deposition methods of these materials, for the low-molecular material, a dry method such as a vacuum evaporation method is used. For the polymer material, a discharge printing method such as spin coating, inkjet, and nozzle-jet or a plate printing method such as flexo printing, screen printing, gravure printing, and reverse printing is used.
Among these methods, the dry method such as a vacuum evaporation method is free from the need to dissolve the functional layer material in a solvent and therefore has e.g. an advantage that a step of removing the solvent is unnecessary. However, it is difficult to apply the material onto the respective different areas separately by using a metal mask. Therefore, the dry method is unsuitable for size increase and mass production of the panel particularly in terms of the facility manufacturing cost. So, the printing system, which is capable of addressing size increase and mass production of the panel comparatively easily, is attracting attention.
In a film deposition method based on the printing system, specifically a lower electrode is formed for each pixel over a circuit board including a thin film transistor (TFT) and so forth and thereafter a pixel isolating film (so-called bank) having apertures opposed to the lower electrodes is formed. Then, lyophobic treatment is performed for the deposited pixel isolating film and thereafter a solution containing the above-described functional layer material is applied and dried. Thereby, a functional layer can be formed in each aperture. However, if the functional layer is formed through the step of applying and drying a solution, the functional layer is thinned in the drying near the interface between the pixel isolating film and the lower electrode because the wettability is different between them. This causes the occurrence of electrical short-circuiting, which leads to a problem of the deterioration of the displayed-image quality.
So, there has been proposed a method in which an inorganic material layer is additionally provided between the above-described pixel isolating film and lower electrode (two-layer structure is employed as the bank structure) to thereby prevent the thinned part generated in the drying step from getting contact with the lower electrode (refer to e.g. Japanese Patent Laid-Open No. 2003-249375 and Japanese Patent Laid-Open No. 2005-326799 (hereinafter referred to as Patent Documents 1 and 2)).